The present invention relates to a method and means for carrying out the rock bolting of a roof or a hanging wall in a mine, a shaft, a tunnel, or generally in any cavity in the rock, by means of bolts which are fastened in boreholes. The invention may also be applied in cases where it is desired to establish in the roof, or on the wall, a means for attaching a hook, loop, or some other device which will be subjected to heavy loads and which, therefore, must be safely anchored.
The general method of fastening bolts in boreholes has been practiced for a long time. The earlier method fundamentally comprised inserting an apertured tubular member having a smaller diameter than the borehole diameter and containing a cement, mortar, or similar bonding material, into the borehole, and thereafter introducing a bolt having a smaller diameter than said tubular member into the tubular member to force the mortar out through the apertures thereof. Besides filling the annular space between the bolt and the tubular member, the mortar will also fill the annular space between the tubular member and the borehole wall, and after setting it will form a hard body which will rigidly bond and anchor the bolt within the rock at least along a substantial portion of its length.
The currently preferred method for bonding a rock bolt within a borehole is to use an adhesive cartridge which is inserted into the borehole. The adhesive cartridge is ruptured in the borehole to produce a resin adhesive which then hardens to bond the bolt in the borehole. The cartridge contains a plurality of chemical components comprising at least a resin component and a hardener component. These components must be intermixed in the borehole in order to interreact to produce a hardenable adhesive. Generally, the adhesive may comprise a base resin, a hardening compound, and inert filler. In order to assure that the chemical components do not interreact with each other to produce the hardenable adhesive before placement of the cartridge and the rock bolt into the borehole, the reactive components are conventionally isolated from each other within the cartridge. Isolation of the components is accomplished by separating the components from each other by one or more frangible partitions within the cartridge. Penetration of the cartridge by the rock bolt will cause rupture of the cartridge and rupture of the frangible partitions. As the rock bolt progresses into the cartridge, it causes intermixing of the various components so that the components will react with each other to produce the hardenable resin adhesive. Within a short time, the resin adhesive sets or hardens and thereby bonds the rock bolt firmly within the borehole.
The insertion of the cartridge within the borehole is easy if the borehole slants downwardly. However, if the borehole slants upwardly, or is overhead in the roof of the tunnel or mine, difficulty is experienced because the cartridge can fall out of the borehole before the bolt is inserted. Thus, the workers in the mine must hold the cartridge in the hole manually while trying to put the bolt in. This is labor intensive and does not lend itself easily to automation.
Accordingly, it is an object of the present invention to provide a novel method for anchoring a rock bolt or the like within a borehole which provides improved efficiency over the prior techniques.
It is a further object of the present invention to provide a novel anchoring device for use with a rock bolt and the like.
These and other objects of the invention, as well as the advantages thereof, will become more clear from the disclosure which follows.